1. Field of the Invention
The invention relates to a rolling shutter slat or bar.
2. Description of the Prior Art
Compared with rolling shutter bars of metal, platic bars are among other things cheaper, lighter and provide better thermal insulation but do have disadvantages. Thus, they are relatively less stiff under wind pressure and suction; furthermore, the coloring of the plastic must take account of the fact that it may under sunshine become hot to such an extent that the plastic is deformed.
These two disadvantages are remedied in a known rolling shutter bar (DE-AS No. 2,622,905) since the weather-side of the hollow profile is coated with a metal layer.
By suitable surface coating or treatment this metal layer may have a desired color but is nevertheless able to reflect sunlight to such an extent that there is no danger of any detrimental warming of the hollow profile section.
To improve the resistance to bending of the rolling shutter slat it was previously necessary to angle the metal layer towards the building side of the rolling shutter bar in order to form a relatively flexurally stiff metal profile which in turn reinforces the hollow profile.
However, any angled portion of the metal layer required for the necessary resistance to bending simultaneously forms a heat bridge which drastically increases the thermal conduction between the side facing the building and the outdoor side of the rolling shutter bar. This is contrary to one of the basic purposes of a rolling shutter, i.e. providing an effective thermal insulation in heating periods to reduce heat losses through the window.